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1. General Principles & Basic Science MCQs

Practice Set 613 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 12241

Topic: 1. General Principles & Basic Science

Articular cartilage is a highly specialized tissue designed to distribute mechanical loads. While water is the most abundant component, which of the following macromolecules is primarily responsible for providing the tensile strength of articular cartilage?

. Aggrecan
. Type I collagen
. Hyaluronic acid
. Chondroitin sulfate
. Type II collagen

Correct Answer & Explanation

. Aggrecan

Explanation

Type II collagen is the primary collagenous component (making up 90-95% of the collagen) in articular cartilage and forms a fibrillar network that provides the tissue with its tensile strength and resistance to shear forces. Proteoglycans (such as aggrecan) draw in water via osmotic pressure, providing compressive stiffness.

Question 12242

Topic: Biomechanics & Biomaterials
In total hip arthroplasty, the use of highly cross-linked polyethylene significantly improves implant longevity primarily by reducing which specific type of wear?
. Adhesive wear
. Abrasive wear
. Third-body wear
. Fatigue wear
. Corrosive wear

Correct Answer & Explanation

. Adhesive wear

Explanation

Highly cross-linked polyethylene primarily decreases adhesive wear, which is the main mechanism of volumetric wear in standard ultra-high-molecular-weight polyethylene (UHMWPE) bearings. The cross-linking process restricts polymer chain mobility. Note that while wear resistance increases, fatigue strength may decrease slightly.

Question 12243

Topic: Biology, Genetics & Bone Healing

Which of the following processes accurately characterizes intramembranous ossification during bone formation?

. Bone formation via an intermediate cartilage model
. Direct differentiation of mesenchymal stem cells into osteoblasts
. Endochondral ossification occurring in a secondary fracture callus
. Longitudinal growth occurring at the physis
. Secondary bone healing facilitated by micro-motion

Correct Answer & Explanation

. Bone formation via an intermediate cartilage model

Explanation

Intramembranous ossification involves the direct differentiation of mesenchymal stem cells into osteoblasts, bypassing any cartilaginous intermediate. This process forms the flat bones of the skull, the clavicle, and the periosteal outer layer of long bones (appositional growth).

Question 12244

Topic: Biology, Genetics & Bone Healing

Denosumab is an effective targeted medical therapy used in the treatment of Giant Cell Tumor of Bone. It exerts its effect by binding directly to which of the following molecules?

. RANK
. RANKL
. Osteoprotegerin
. Cathepsin K
. TNF-alpha

Correct Answer & Explanation

. RANK

Explanation

Denosumab is a fully human monoclonal antibody that binds directly to RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand). In Giant Cell Tumor of Bone, the neoplastic mononuclear stromal cells overexpress RANKL, which recruits and activates the reactive osteoclast-like giant cells. Denosumab blocks this interaction.

Question 12245

Topic: 1. General Principles & Basic Science
According to the Snyder classification, a Type II SLAP (Superior Labrum Anterior to Posterior) tear is best characterized by which of the following descriptions?
. Fraying of the superior labrum with a firmly attached biceps anchor
. Detachment of both the superior labrum and the biceps anchor from the superior glenoid
. A bucket-handle tear of the superior labrum with an intact biceps anchor
. A bucket-handle tear of the superior labrum extending into the long head of the biceps tendon
. Anteroinferior detachment of the labrum extending to the 6 o'clock position

Correct Answer & Explanation

. Detachment of both the superior labrum and the biceps anchor from the superior glenoid

Explanation

Type II SLAP lesions involve the detachment of the superior labrum and the origin of the long head of the biceps tendon from the superior glenoid tubercle, resulting in a pathological instability of the biceps-labral complex. Type I is fraying; Type III is a bucket-handle tear with an intact anchor; Type IV is a bucket-handle tear extending into the biceps tendon.

Question 12246

Topic: 1. General Principles & Basic Science
Which specific type of collagen is the predominant structural protein in articular hyaline cartilage, responsible for its tensile strength?
. Type I
. Type II
. Type III
. Type IX
. Type X

Correct Answer & Explanation

. Type II

Explanation

Type II collagen makes up 90-95% of the collagen found in articular (hyaline) cartilage and provides the structural framework that resists tensile and shear forces. Type I collagen is predominant in bone, tendon, and fibrocartilage (e.g., meniscus). Type X is found in the hypertrophic zone of the epiphyseal plate.

Question 12247

Topic: Biology, Genetics & Bone Healing

Which of the following bone grafting materials inherently possesses osteogenic, osteoinductive, and osteoconductive properties?

. Demineralized bone matrix (DBM)
. Cancellous bone allograft
. Iliac crest bone autograft
. Bone morphogenetic protein-2 (BMP-2)
. Calcium phosphate cement

Correct Answer & Explanation

. Demineralized bone matrix (DBM)

Explanation

Iliac crest bone autograft is the 'gold standard' because it is the only option listed that provides all three essential properties for bone healing: osteoconduction (scaffold), osteoinduction (growth factors like BMPs), and osteogenesis (live osteoprogenitor cells). DBM is osteoconductive and osteoinductive but lacks live cells. Allograft is only osteoconductive. BMP-2 is purely osteoinductive.

Question 12248

Topic: 1. General Principles & Basic Science

In healthy articular cartilage, which structural zone is characterized by collagen fibers aligned perpendicular to the joint surface and contains the highest concentration of proteoglycans?

. Superficial zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified cartilage zone
. Tidemark

Correct Answer & Explanation

. Superficial zone

Explanation

The deep (radial) zone of articular cartilage is characterized by thick collagen fibers (primarily Type II) aligned perpendicularly to the articular surface. This zone provides the greatest resistance to compressive forces due to its high concentration of water-retaining proteoglycans.

Question 12249

Topic: Biology, Genetics & Bone Healing

A 32-year-old female presents with a lytic, eccentrically located lesion in the distal femoral epiphysis. Biopsy confirms a Giant Cell Tumor of bone. She is treated preoperatively with denosumab to consolidate the tumor and reduce its vascularity. What is the specific molecular target of this medication?

. Vascular endothelial growth factor (VEGF)
. Receptor activator of nuclear factor kappa-B ligand (RANKL)
. Osteoclastic proton pumps
. Hydroxyapatite crystals
. CD20 receptor

Correct Answer & Explanation

. Vascular endothelial growth factor (VEGF)

Explanation

Denosumab is a human monoclonal antibody that binds to RANKL, preventing it from activating RANK on the surface of osteoclasts. In Giant Cell Tumor of bone, the neoplastic stromal cells express RANKL, which recruits and activates the reactive, bone-destroying multinucleated giant cells.

Question 12250

Topic: Biology, Genetics & Bone Healing
During the normal biological process of tendon healing, which of the following best describes the predominant collagen type synthesized and deposited during the early proliferative phase (typically days 5 to 28)?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type III collagen

Explanation

Tendon healing occurs in overlapping phases: inflammatory, proliferative, and remodeling. During the proliferative phase, fibroblasts primarily synthesize Type III collagen, which forms a disorganized extracellular matrix. During the later remodeling phase, this is gradually replaced by the stronger, highly organized Type I collagen.

Question 12251

Topic: Biology, Genetics & Bone Healing

A 45-year-old male sustains a midshaft tibial fracture. Which of the following cytokines is primarily responsible for the initial recruitment of mesenchymal stem cells to the fracture site?

. Bone morphogenetic protein-2 (BMP-2)
. Platelet-derived growth factor (PDGF)
. Interleukin-1 (IL-1)
. Tumor necrosis factor-alpha (TNF-alpha)
. Vascular endothelial growth factor (VEGF)

Correct Answer & Explanation

. Bone morphogenetic protein-2 (BMP-2)

Explanation

PDGF is released from degranulating platelets in the fracture hematoma immediately after injury. It acts as a powerful chemoattractant and mitogen for mesenchymal stem cells, initiating the healing cascade.

Question 12252

Topic: Biomechanics & Biomaterials

During revision of a failed internal fixation, a surgeon contemplates using titanium screws in conjunction with a stainless steel plate. Which of the following biomaterial principles makes this combination potentially problematic?

. Titanium is significantly stiffer than stainless steel
. Galvanic corrosion may occur due to differing anodic indices
. Crevice corrosion is prevented by combining dissimilar metals
. Stainless steel induces rapid osteolysis when contacting titanium
. Titanium prevents the formation of a passivation layer on stainless steel

Correct Answer & Explanation

. Titanium is significantly stiffer than stainless steel

Explanation

Mixing dissimilar metals, such as stainless steel and titanium, in an electrolytic environment (like the human body) can lead to galvanic corrosion. The less noble metal acts as an anode and corrodes at an accelerated rate.

Question 12253

Topic: Surgical Anatomy & Approaches

A posterior approach to the shoulder requires careful identification and protection of the axillary nerve and posterior circumflex humeral artery as they exit the axilla to innervate the deltoid. Through which of the following spaces do these structures pass, and what are its boundaries?

. Triangular space; bounded by the teres minor, teres major, and long head of triceps
. Triangular interval; bounded by the teres major, long head of triceps, and lateral head of triceps
. Quadrangular space; bounded by the teres minor superiorly, teres major inferiorly, long head of triceps medially, and surgical neck of humerus laterally
. Quadrangular space; bounded by the teres major superiorly, teres minor inferiorly, long head of triceps medially, and humeral shaft laterally
. Rotator interval; bounded by the supraspinatus, subscapularis, and coracoid process

Correct Answer & Explanation

. Triangular space; bounded by the teres minor, teres major, and long head of triceps

Explanation

The axillary nerve and posterior circumflex humeral vessels exit the axilla through the quadrangular space. The boundaries are the teres minor (superiorly), teres major (inferiorly), long head of the triceps (medially), and surgical neck of the humerus (laterally). The triangular space transmits the circumflex scapular artery. The triangular interval transmits the radial nerve and profunda brachii artery.

Question 12254

Topic: Surgical Anatomy & Approaches

The anterior (Smith-Petersen) approach to the hip is historically lauded for utilizing a true internervous plane. Which two nerves supply the superficial muscles that define this plane?

. Femoral nerve and Superior gluteal nerve
. Femoral nerve and Obturator nerve
. Superior gluteal nerve and Inferior gluteal nerve
. Femoral nerve and Sciatic nerve
. Obturator nerve and Sciatic nerve

Correct Answer & Explanation

. Femoral nerve and Superior gluteal nerve

Explanation

The superficial internervous plane of the Smith-Petersen approach runs between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve). The deep plane lies between the rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).

Question 12255

Topic: Surgical Anatomy & Approaches

The anterolateral (Watson-Jones) approach to the hip is frequently used for total hip arthroplasty. The superficial plane is developed between the tensor fasciae latae (TFL) and the gluteus medius. Why is this considered an intermuscular plane rather than a true internervous plane?

. Both muscles are innervated by the femoral nerve
. Both muscles are innervated by the superior gluteal nerve
. Both muscles are innervated by the inferior gluteal nerve
. The plane crosses the dermatomal boundary of L4 and L5
. The TFL is primarily a fascial structure without direct motor innervation

Correct Answer & Explanation

. Both muscles are innervated by the femoral nerve

Explanation

The Watson-Jones approach utilizes an intermuscular plane between the tensor fasciae latae and the gluteus medius. Since both of these muscles are innervated by the superior gluteal nerve, it is not a true internervous plane. Care must be taken not to split the muscles too proximally to avoid injury to the superior gluteal neurovascular bundle.

Question 12256

Topic: Infection, Pharmacology & VTE

During a medial approach to the proximal tibia, the pes anserinus is encountered. Which of the following represents the correct anterior-to-posterior orientation of the tendinous insertions forming the pes anserinus?

. Sartorius, Gracilis, Semitendinosus
. Gracilis, Sartorius, Semitendinosus
. Semitendinosus, Gracilis, Sartorius
. Sartorius, Semitendinosus, Gracilis
. Gracilis, Semitendinosus, Sartorius

Correct Answer & Explanation

. Sartorius, Gracilis, Semitendinosus

Explanation

The pes anserinus ('goose foot') consists of the combined tendinous insertions of the Sartorius, Gracilis, and Semitendinosus on the proximal anteromedial tibia. They insert in that exact anterior-to-posterior and proximal-to-distal order. A common mnemonic is 'Say Grace Before Tea' (Sartorius, Gracilis, Semitendinosus).

Question 12257

Topic: Surgical Anatomy & Approaches

In evaluating a patient with refractory posterior hip/buttock pain and sciatica with no identifiable lumbar spine pathology, piriformis syndrome is suspected. In the most common anatomical configuration (over 80% of individuals), how does the sciatic nerve pass in relation to the piriformis muscle?

. The entire sciatic nerve passes superior to the piriformis
. The entire sciatic nerve passes inferior to the piriformis
. The common peroneal division passes through the piriformis, and the tibial division passes inferior
. The common peroneal division passes superior, and the tibial division passes inferior
. The entire sciatic nerve pierces the belly of the piriformis

Correct Answer & Explanation

. The entire sciatic nerve passes superior to the piriformis

Explanation

In approximately 80-85% of the population, the entire sciatic nerve exits the pelvis via the greater sciatic foramen passing deep (inferior) to the piriformis muscle. The most common anatomical variant (approx. 10-12%) occurs when the common peroneal division pieces the piriformis muscle while the tibial division passes inferior to it.

Question 12258

Topic: Surgical Anatomy & Approaches

The suboccipital triangle is a critical anatomical landmark during posterior surgical approaches to the craniovertebral junction, as it contains the V3 segment of the vertebral artery and the suboccipital nerve (C1). Which of the following muscles does NOT form a boundary of the suboccipital triangle?

. Rectus capitis posterior major
. Obliquus capitis superior
. Obliquus capitis inferior
. Rectus capitis posterior minor
. None of the above; all form the boundaries

Correct Answer & Explanation

. Rectus capitis posterior major

Explanation

The boundaries of the suboccipital triangle are formed by three muscles: the rectus capitis posterior major (superomedial border), the obliquus capitis superior (superolateral border), and the obliquus capitis inferior (inferolateral border). The rectus capitis posterior minor lies medial to the rectus capitis posterior major and is not a boundary of the triangle.

Question 12259

Topic: Surgical Anatomy & Approaches

A surgeon is performing an open reduction and internal fixation (ORIF) of a middle-third humeral shaft fracture via a posterior approach. The radial nerve is identified in the spiral groove. Moving distally, the nerve pierces the lateral intermuscular septum to enter the anterior compartment of the arm. At approximately what distance proximal to the lateral epicondyle does this transition occur?

. 5 cm
. 10 cm
. 15 cm
. 20 cm
. 2 cm

Correct Answer & Explanation

. 5 cm

Explanation

The radial nerve passes from the posterior compartment to the anterior compartment by piercing the lateral intermuscular septum approximately 10 to 12 cm proximal to the lateral epicondyle. Knowledge of this distance is critical during lateral or posterior plating of the humerus to safely localize and protect the radial nerve.

Question 12260

Topic: Surgical Anatomy & Approaches

During an ilioinguinal approach for a displaced acetabular fracture, a significant bleeding source is encountered near the superior pubic ramus. This vessel, known as the 'corona mortis', represents an anatomical anastomosis between which two vascular systems?

. The internal pudendal and the obturator artery
. The obturator system and the external iliac or inferior epigastric system
. The superior gluteal and the inferior gluteal artery
. The internal iliac and the external iliac arteries directly
. The femoral artery and the obturator artery

Correct Answer & Explanation

. The internal pudendal and the obturator artery

Explanation

The corona mortis ('crown of death') is a vascular connection between the obturator (internal iliac) and the external iliac or inferior epigastric vessels. It crosses the superior pubic ramus and is at high risk of iatrogenic injury during anterior pelvic approaches, such as the ilioinguinal or Stoppa approach.

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